"Last month, our incredible employees braved subzero temperatures and peak holiday loads to lead United into first place among competitors in mainline on-time departures, completion factor and on-time arrivals," said Scott Kirby, president of United Airlines. "It was the best-ever December for our operation, putting us in a great position to continue to deliver a solid operation for our customers as we head into 2018."

The company now expects fourth-quarter 2017 consolidated passenger unit revenue to be about flat compared to the fourth quarter of 2016, driven by stronger yields and better close-in demand.